eDNA sampling for great crested newts and its window

An eDNA survey for great crested newts can only be carried out between 15 April and 30 June. That window is fixed by the national protocol the laboratories work to, and a sample taken on 1 July is worthless however good the pond looks. If you are building on a site with ponds nearby and you miss the window, your options narrow to waiting a year or using a district level licence.

The test itself is inexpensive by ecology standards and quick to turn round. Everything that follows a positive result is neither.

What an eDNA test establishes and what it does not

Environmental DNA sampling looks for traces of great crested newt DNA shed into the water. A laboratory run against a validated protocol returns a presence or absence result for that pond in that season.

That is the whole output. It gives no population size class, no indication of how many animals are present, no information about where they breed within the pond, and nothing at all about terrestrial habitat use. A council or a licensing body deciding whether a scheme needs mitigation, and how much, needs more than presence.

So the test earns its place as a screening tool. It rules ponds out at low cost so that expensive survey effort goes only where newts are actually present. Used the other way round, as a substitute for population survey, it will be sent back.

The sampling window and why it is fixed

The window runs from 15 April to 30 June because that is when adult newts are reliably in the water breeding and shedding detectable material. Before mid-April the animals may not have arrived. After the end of June they begin to leave, and detection rates fall away fast enough that a negative result stops meaning anything.

The sample must be collected using an approved kit, following the standard method: twenty sub-samples taken evenly around the accessible pond margin, combined, mixed and preserved, then sent to a laboratory that has passed the relevant proficiency testing. Kits have a shelf life and a temperature tolerance. Samples that sit in a van boot for a weekend produce inconclusive results, and inconclusive counts as a failed test rather than a negative.

One sampling visit per pond per season is the norm. Collectors do not have to hold a newt licence to take an eDNA sample, because sampling water is not a licensable activity, although a competent ecologist should design the survey and interpret it.

Which ponds to sample and the search radius

The standard starting point is every pond within 250 metres of the development boundary, measured as the distance an animal would travel rather than as the crow flies where a barrier intervenes. Where habitat connectivity is strong, or where the scheme is large, 500 metres is often used instead.

Barriers matter. A dual carriageway, a wide river or a continuous industrial estate between a pond and your site reduces the likelihood of newts reaching it, and that argument belongs in the report with the reasoning shown. Absence of access is a separate problem. Where a landowner refuses entry to a pond, say so, assume presence as a precaution, and explain the assumption rather than quietly dropping the pond from the schedule.

Ponds that dry out before mid-summer in most years, heavily shaded ponds and ponds stocked with fish are less likely to support breeding, which is where habitat scoring comes in.

Habitat suitability scoring before you spend money

The habitat suitability index scores a pond against ten factors including geographic location, pond area, permanence, water quality, shade, waterfowl, fish, the number of ponds nearby, terrestrial habitat quality and macrophyte cover. The result is a single figure between zero and one, banded from poor through below average, average and good to excellent.

Run the scoring first. A shaded, fish-stocked pond in a car park scoring poorly can often be discounted with a short justification, saving the cost of sampling. A pond scoring well in a cluster of other ponds tells you to budget for the full survey sequence from the start.

The index predicts suitability rather than presence, so a poor score is a reason to deprioritise a pond rather than a reason to declare it newt-free. Councils and Natural England both read it that way.

Reading a negative and a positive result

A negative eDNA result from a properly collected sample within the window is good evidence that the pond did not hold breeding newts that season. It is not permanent. Most authorities treat a negative as valid for the season it was taken in, sometimes two, so a result from three years ago will be challenged on a live application.

A positive result establishes presence and nothing more. The next question is how the development affects the population, and that needs a population size class assessment: four to six survey visits using a combination of torch counts, bottle trapping, egg searching and netting, carried out between mid-March and mid-June with at least half of them falling between mid-April and mid-May. Those visits require a survey licence from Natural England.

At that point you are into the offence provisions. Great crested newts are protected under the Conservation of Habitats and Species Regulations 2017 and the Wildlife and Countryside Act 1981, and deliberate capture, killing, disturbance or damage to a breeding site or resting place is an offence. A mitigation licence must be applied for by a suitably licensed ecologist, and the three licensing tests have to be met. The Protected Species Survey is the report that carries this work, and a licensed ecologist is legally required for it. A PlanScope draft is a starting point for that professional rather than a substitute.

Planning around a missed window

Three routes exist when the window has gone.

Wait until the following April. Honest, and often unacceptable to a programme.

Use district level licensing where your local authority area is covered. Under that scheme the developer pays a conservation payment based on the impact, calculated from habitat present rather than from site survey, and Natural England delivers compensation strategically through new and restored ponds. It removes the need for site-specific newt survey in many cases, and it is the route most small housebuilders now take.

Or assume presence. Where the site is small and the affected habitat is limited, an ecologist can sometimes advise a precautionary approach with method statements and supervision, agreed with the council by condition. That works less often than applicants hope, and it does not remove the need for a licence where an offence would otherwise occur.

Whichever route you choose, commission a Preliminary Ecological Appraisal in the autumn or winter before you want to build. It costs little, it identifies every survey window you will need, and it is the document that stops an ecology constraint becoming a twelve-month delay. Newt work also interacts with your Biodiversity Net Gain Assessment, because ponds and their margins are habitats on the statutory metric as well as newt habitat.

But do not clear the site first to simplify the survey. Destroying habitat ahead of an application is both an offence risk and the fastest way to lose the council's goodwill.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

You can see which ecology reports your site is likely to need from a postcode. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.